1266207817081 has 3 divisors (see below), whose sum is σ = 1266208942341. Its totient is φ = 1266206691822.

The previous prime is 1266207817057. The next prime is 1266207817093. The reversal of 1266207817081 is 1807187026621.

The square root of 1266207817081 is 1125259.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 1266207817081 - 2¹⁵ = 1266207784313 is a prime.

It is a super-2 number, since 2×1266207817081² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1266207817681) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 562630 + ... + 1687888.

It is an arithmetic number, because the mean of its divisors is an integer number (422069647447).

Almost surely, 2^{1266207817081} is an apocalyptic number.

1266207817081 is the 1125259-th square number.

1266207817081 is the 562630-th centered octagonal number.

It is an amenable number.

1266207817081 is a deficient number, since it is larger than the sum of its proper divisors (1125260).

1266207817081 is an frugal number, since it uses more digits than its factorization.

1266207817081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2250518 (or 1125259 counting only the distinct ones).

The product of its (nonzero) digits is 451584, while the sum is 49.

Multiplying 1266207817081 by its sum of digits (49), we get a square (62044183036969 = 7876813²).

The spelling of 1266207817081 in words is "one trillion, two hundred sixty-six billion, two hundred seven million, eight hundred seventeen thousand, eighty-one".